Intervertebral disc nucleus implants and methods

ABSTRACT

Nucleus pulposus implants that are resistant to migration in and/or expulsion from an intervertebral disc space are provided. In one form of the invention, an implant includes a load bearing elastic body surrounded in the disc space by an anchoring, preferably resorbable, outer shell. In certain forms of the invention, the elastic body is surrounded by a supporting member, such as a band or jacket, and the supporting member is surrounded by the outer shell. Kits for forming such implants are also provided. In another form of the invention, an implant is provided that has locking features and optional shape memory characteristics. In yet another aspect of the invention, nucleus pulposus implants are provided that have shape memory characteristics and are configured to allow short-term manual, or other deformation without permanent deformation, cracks, tears, breakage or other damage. Methods of forming and implanting the implants are also described, as are delivery devices and components thereof for delivering the implants.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part, and claims thebenefit, of pending U.S. patent application Ser. No. 09/650,525, filedAug. 30, 2000, which is hereby incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to nucleus pulposus implants andmethods for their implantation.

[0003] The intervertebral disc functions to stabilize the spine and todistribute forces between vertebral bodies. A normal disc includes agelatinous nucleus pulposus, an annulus fibrosis and two vertebral endplates. The nucleus pulposus is surrounded and confined by the annulusfibrosis.

[0004] Intervertebral discs may be displaced or damaged due to trauma ordisease. Disruption of the annulus fibrosis may allow the nucleuspulposus to protrude into the vertebral canal, a condition commonlyreferred to as a herniated or ruptured disc. The extruded nucleuspulposus may press on a spinal nerve, which may result in nerve damage,pain, numbness, muscle weakness and paralysis. Intervertebral discs mayalso deteriorate due to the normal aging process. As a disc dehydratesand hardens, the disc space height will be reduced, leading toinstability of the spine, decreased mobility and pain.

[0005] One way to relieve the symptoms of these conditions is bysurgical removal of a portion or all of the intervertebral disc. Theremoval of the damaged or unhealthy disc may allow the disc space tocollapse, which would lead to instability of the spine, abnormal jointmechanics, nerve damage, as well as severe pain. Therefore, afterremoval of the disc, adjacent vertebrae are typically fused to preservethe disc space. Several devices exist to fill an intervertebral spacefollowing removal of all or part of the intervertebral disc in order toprevent disc space collapse and to promote fusion of adjacent vertebraesurrounding the disc space. Even though a certain degree of success withthese devices has been achieved, full motion is typically never regainedafter such vertebral fusions. Attempts to overcome these problems haveled to the development of disc replacements. Many of these devices arecomplicated, bulky and made of a combination of metallic and elastomericcomponents. Thus, such devices require invasive surgical procedures andtypically never fully return the full range of motion desired.

[0006] More recently, efforts have been directed to replacing thenucleus pulposus of the disc with a similar gelatinous material, such asa hydrogel. However, there exists a possibility of tearing or otherwisedamaging the hydrogel implant during implantation. Moreover, oncepositioned in the disc space, many hydrogel implants may migrate in thedisc space and/or may be expelled from the disc space through an annulardefect, or other annular opening. A need therefore exists for moredurable implants, as well as implants that are resistant to migrationand/or expulsion through an opening in the annulus fibrosis. The presentinvention addresses these needs.

SUMMARY OF THE INVENTION

[0007] Nucleus pulposus implants that are resistant to migration inand/or expulsion from an intervertebral disc space are provided.Accordingly, in one aspect of the invention, nucleus pulposus implantsare provided that include a load bearing elastic body sized forintroduction into an intervertebral disc space and surrounded by aresorbable shell that provides the initial fixation for the elastic bodywithin the disc space. The implant may include various surface featureson its outer surface, including surface configurations or chemicalmodifications, that enhance the bonding between the outer surface of theimplants and the resorbable shell. Kits for forming such implants arealso provided. In other forms of the invention, the elastic body may besurrounded by a supporting member wherein the supporting member issurrounded by the resorbable shell.

[0008] In yet another aspect of the invention, nucleus pulposus implantsare provided that have shape memory and are configured to allowextensive short-term deformation without permanent deformation, cracks,tears or other breakage. In one form of the invention, an implantincludes a load bearing elastic body sized for placement into anintervertebral disc space. The body includes a first end, a second endand a central portion wherein the first end and second end arepositioned, in a folded, relaxed configuration, adjacent to the centralportion to form at least one inner fold. The inner fold preferablydefines an aperture. The elastic body is deformable into a second,straightened, non-relaxed, unfolded configuration for insertion throughan opening in an intervertebral disc annulus fibrosis. The elastic bodyis deformable automatically back into a folded configuration after beingplaced in the intervertebral disc space. Advantageously, where theimplant having shape memory is formed of a hydrogel material, or otherhydrophilic material that may be dehydrated, the implant may be fully orpartially dehydrated prior to insertion such that it may be insertedthrough a relatively small opening in the annulus fibrosis. The openingmay, for example, be a pre-existing defect or may be made by making asmall incision.

[0009] In still other aspects of the invention, nucleus pulposusimplants having locking features and optionally having shape memory areprovided. In one embodiment, an implant includes a load bearing elasticbody having a first end and a second end that are configured for matingengagement with each other. The implant has a first, lockedconfiguration wherein the first and second ends are matingly engaged toeach other. The implant may be configured into a second, straightenedconfiguration by application of external force for insertion through anopening in an intervertebral disc annulus fibrosis. When the implantincludes shape memory characteristics, it may be automaticallyconfigured, or otherwise returned, back into its first, lockedconfiguration after insertion through the opening in the annulusfibrosis and after any external force is removed, or may be placed intoits locked configuration by application of external force.

[0010] In other aspects of the invention, methods of implanting thenucleus pulposus implants of the present invention are provided. In onemode of carrying out the invention, a method includes providing theappropriate implant, preparing the intervertebral disc space to receivethe implant and then placing the implant into the intervertebral discspace. Where the implant includes a load bearing elastic body and anouter resorbable shell, a preferred method includes preparing theintervertebral disc space to receive the implant, introducing theelastic body forming the core of the implant into the disc space whereinthe body is surrounded in the disc space by a resorbable outer shell.The material forming the resorbable shell may be placed in the discspace prior to, after, or at the same time as insertion of the elasticbody. Alternatively, the elastic body may be surrounded by the outershell prior to introduction of the elastic body into the intervertebraldisc space.

[0011] In further aspects, a spinal disc implant delivery device isprovided. In one form, the device includes a base member having aproximal end, a distal end and a lumen extending longitudinallytherethrough; a plurality of movable members having a proximal end and adistal end; and an elongated member having a proximal end and a distalend and a lumen extending longitudinally therethrough. The proximal endof the movable members abut the distal end of the base member. Theproximal end of the base member is matingly engaged to the distal end ofthe elongated member. Moreover, the movable members have a closedconfiguration that defines a cavity in communication with the lumen ofthe base member.

[0012] In further aspects of the invention, a spinal disc implantdelivery device tip is provided that includes a base member and movablemembers as described above.

[0013] In other forms of the invention, a spinal disc implant deliverydevice includes an elongated housing member having a proximal end, adistal end and a lumen extending longitudinally therethrough and a tipmember. The tip member advantageously has a top wall, a bottom wall, afirst side wall, a second side wall, a proximal end, and a distal end.The walls of the tip member preferably define a lumen extendinglongitudinally therethrough. The proximal end of the tip member may beconnected to the distal end of the elongated housing member.Additionally, the tip member is sized and configured for delivery of aspinal disc implant through an aperture in an annulus fibrosis. Thelumen of the tip member is preferably in fluid communication with thelumen of the elongated housing member.

[0014] In other forms of the invention, the top wall and bottom wallinclude an opening therethrough that extends from the proximal end ofthe tip member to the distal end of the tip member.

[0015] It is an object of the invention to provide nucleus pulposusimplants, and kits for their formation, that are resistant to migrationin and/or explusion from an intervertebral disc space.

[0016] It is a further object of the invention to provide nucleuspulposus implants having shape memory that are configured to allowextensive short term manual, or other deformation without permanentdeformation, cracks, tears, breakage or other damage.

[0017] It is yet another object of the present invention to providenucleus pulposus implants having locking features.

[0018] It is a further object of the present invention to providemethods of forming and implanting the nucleus pulposus implantsdescribed herein, as well as spinal implant delivery devices or toolsfor implanting the implants.

[0019] These and other objects and advantages of the present inventionwill be apparent from the description herein.

BRIEF DESCRIPTION OF THE FIGURES

[0020]FIG. 1 depicts a side view of a cross-section of a nucleuspulposus implant, including an elastic body 15 surrounded by ananchoring outer shell 30, implanted in the intervertebral disc space ofa disc.

[0021]FIG. 2 depicts a top, cross-sectional view of the nucleus pulposusimplant of FIG. 1.

[0022]FIG. 3 depicts a side view of a cross-section of the nucleuspulposus implant of FIG. 1 after outer shell 30 has been resorbed andreplaced by fibrous scar tissue 33.

[0023]FIG. 4 shows a top, cross-sectional view of the nucleus pulposusimplant of FIG. 3.

[0024]FIG. 5 shows a side view of a cross-section of a nucleus pulposusimplant, including an elastic body 15 surrounded by a supporting member34, in the form of a band, wherein the supporting member is surroundedby an anchoring outer shell 30, implanted in the intervertebral discspace of a disc.

[0025]FIG. 6 depicts a side view of a cross-section of a nucleuspulposus implant, including an elastic body 15 surrounded by asupporting member 37, in the form of a jacket, wherein the supportingmember is surrounded by an anchoring outer shell 30, implanted in theintervertebral disc space of a disc.

[0026] FIGS. 7A-7D depict various patterns of a supporting member of thepresent invention.

[0027]FIG. 8 depicts a side view of a cross-section of a nucleuspulposus implant including an elastic body 15 surrounded by a supportingmember 34, taking the form of a band, that is further reinforced, orotherwise supported, by straps 420 and 430. The implant is surrounded byan anchoring outer shell 30 and is shown implanted in the intervertebraldisc space of a disc.

[0028]FIG. 9 shows a top, cross-sectional view of the nucleus pulposusimplant of FIG. 8.

[0029]FIG. 10 depicts a side view of an alternative embodiment of anucleus pulposus implant of the present invention that includesperipheral supporting band 34″ and securing straps 520, 530, 540 and 550and is surrounded by an anchoring outer shell 30 and implanted in theintervertebral disc space of a disc.

[0030]FIG. 11 depicts a top, cross-sectional view of the nucleuspulposus implant of FIG. 10.

[0031]FIG. 12 depicts a top view of an alternative embodiment of anucleus pulposus implant having shape memory.

[0032]FIG. 13 shows a side view of the implant shown in FIG. 12.

[0033] FIGS. 14A-14J depict portions of nucleus pulposus implants withsurface modifications. FIGS. 14A-14H show side views of top portions ofthe implants, and FIG. 14I and FIG. 14J show top views of the viewsshown in 14C and 14D, respectively.

[0034] FIGS. 15A-15N show top views of alternative embodiments ofnucleus pulposus implants having shape memory in folded, relaxedconfigurations.

[0035] FIGS. 16A-16N depict top views of the implants shown in FIGS.15A-15N, respectively, in unfolded, non-relaxed configurations.

[0036]FIG. 17 depicts a top view of an alternative embodiment of anucleus pulposus implant of the present invention having a self-lockingfeature. The implant is shown in its locked, relaxed configuration.

[0037]FIG. 18 depicts a side view of the implant of FIG. 17.

[0038]FIG. 19 depicts a side view of the implant of FIG. 18 in anunfolded, non-locked, non-relaxed configuration.

[0039]FIG. 20 depicts one step in a method of implanting nucleuspulposus implant 40 into intervertebral disc space 20 between vertebrae21 and 22 using a conventional implantation tool 310.

[0040]FIG. 21 depicts a top, cross-sectional view of a nucleus pulposusimplant 10 in its folded, relaxed configuration positioned inintervertebral disc space 20.

[0041] FIGS. 22A-22Q show top views of alternative embodiments ofnucleus pulposus implants having shape memory in folded, relaxedconfigurations.

[0042] FIGS. 23A-23Q depict top views of the implants shown in FIGS.22A-22Q, respectively, in unfolded, non-relaxed configurations.

[0043]FIGS. 24, 25, 26 and 27 depict side views of the implants shown inFIGS. 22I, 22J, 22K and 22N, respectively.

[0044]FIG. 28 depicts a side cross-sectional view of one embodiment of aspinal disc implant delivery tool configured to deliver the shape memoryimplants described herein.

[0045]FIG. 29 depicts a view of another embodiment of a spinal discimplant delivery device showing features of the tip portion.

[0046] FIGS. 30A-30J depict side views of surface features that may bepresent on the surfaces of the tip portions of various spinal discimplant delivery devices described herein.

[0047]FIG. 31 depicts a view of an alternative embodiment of a spinaldisc implant delivery device showing features of the tip portion.

[0048]FIG. 32 depicts how the spinal disc implant delivery device ofFIG. 31 may be used to aid placement of a spinal disc implant.

[0049]FIG. 33 depicts a view of yet a further alternative embodiment ofa spinal disc implant delivery device.

[0050]FIG. 34 depicts a view of yet a further alternative embodiment ofa spinal disc implant delivery device showing features of the tipportion.

[0051]FIG. 35 shows a view of an alternative embodiment of a spinal discimplant delivery device showing features of the tip portion.

[0052]FIG. 36 shows a side view of an alternative embodiment of a spinalimplant delivery device.

[0053]FIG. 37A depicts an end view of the device of FIG. 36, taken alongline 37A-37A.

[0054] FIGS. 37B-37F depict end views of tip portions of the discimplant delivery devices described herein. The tip portions are ofvarious shapes and have variously numbered movable members.

[0055]FIG. 38 depicts a step in the method of implanting the shapememory implants described herein into an intervertebral disc space.

[0056]FIG. 39-44 depict further steps in the method of FIG. 38.

[0057]FIG. 45-48 show top views of how selected spinal disc implantdelivery devices may be positioned in an intervertebral disc space fordelivery of a spinal implant.

[0058]FIG. 49 depicts an end view of the positioned spinal disc implantdelivery device of FIG. 45, taken along line 49-49.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] For the purposes of promoting an understanding of the principlesof the invention, reference will now be made to preferred embodimentsand specific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications of the invention, and such further applications of theprinciples of the invention as illustrated herein, being contemplated aswould normally occur to one skilled in the art to which the inventionrelates.

[0060] The present invention provides prosthetic intervertebral discnucleus pulposus implants that may fully or partially replace thenatural, or native, nucleus pulposus in mammals, including humans andother animals. In one aspect of the invention, implants are providedthat are configured to resist expulsion or other migration through adefect, or other opening, in the annulus fibrosis and to resistexcessive migration within an intervertebral disc space. In certainforms, these implants combine the advantages of an injectable/in-situcuring implant with a pre-formed implant. For example, a nucleuspulposus implant may include a load bearing elastic body surrounded byan outer, preferably resorbable or otherwise temporary, shell. The outershell advantageously anchors the elastic body within the intervertebraldisc space. The surface of the elastic body may include various surfacefeatures, including various macro-surface patterns, and chemical orphysical modifications as described herein to further enhance fixationof the implant to the outer resorbable shell. The surface features, suchas the macro-surface patterns and physical modifications, for example,are also expected to enhance fixation of the elastic body to surroundingtissue such that, in certain forms of the invention, no outer shell maybe needed.

[0061] In other aspects of the invention, nucleus pulposus implantshaving shape memory that are configured to allow extensive short-termmanual or other deformation without permanent deformation, cracks,tears, breakage or other damage are provided. In preferred forms of theinvention wherein the implants are formed from a hydrogel or otherhydrophilic material, the implants can not only pass through arelatively small incision in the annulus fibrosis, but can alsosubstantially fill and conform to the intervertebral disc space. In oneform of the invention, an implant includes a load bearing elastic bodywith shape memory having first and second ends that are positionedadjacent to a central portion to form at least one inner fold. The innerfold desirably defines an aperture or channel.

[0062] In other embodiments of the invention, the shape memory implantsare configured to form a spiral or other annular shape in the discspace, and may also be configured to have ends that matingly engage eachother for further securing the implant in the disc cavity. Methods ofmaking and implanting the implants described herein are also provided.

[0063] As disclosed above, in a first aspect of the invention, a nucleuspulposus implant is provided that includes a load bearing elastic bodysized for introduction into an intervertebral disc space and surroundedby an outer, preferably resorbable, shell. Referring now to FIGS. 1 and2, prosthetic implant 10 includes a core load bearing elastic body 15disposed in intervertebral disc space 20, between vertebral body 21 and22 and surrounded by an outer shell 30. More specifically, elastic body15 has an outer surface 16 in contact with, and preferably bonded to, anouter shell 30 that may advantageously be resorbable, or otherwisetemporary. Outer surface 31 of outer shell 30 preferably conforms to theshape of the intervertebral disc space 20, being in contact with annulusfibrosis 5, and may completely surround elastic body 15 as seen in FIGS.1 and 2, although outer shell 30 may only partially surround elasticbody 15. As an example, upper, lower and/or lateral voids surroundingelastic body 15 may be filled in by outer shell 30, as long as theelastic body is in some way anchored, or otherwise fixed in place, bythe outer shell so as to prevent its expulsion from, or excessivemigration in, the disc cavity. Thus, outer shell 30 may be configured tofill the aforementioned voids. Additionally, inner surface 32 of outershell 30 preferably conforms to the shape of elastic body 15, andpreferably bonds to outer surface 16 of elastic body 15 as discussedbelow. In preferred embodiments, the elastic core and the outer shellsubstantially fill the disc cavity as further discussed below.

[0064] Outer shell 30 not only provides for a properly fit implant 10within intervertebral disc space 20 for maximum load-bearing, stresstransfer, and bonding of the implant surface to the surrounding disctissues for fixation against excessive migration, it also seals anannular defect 18 for further resistance to migration and/or expulsionof the implant. Such sealing of the annular defect may also provideadditional physical and mechanical support to the disc. Furthermore, theinjectable outer shell material may provide intra-operative flexibilityin fitting the core elastic body of implant 10 within the disc space asit may compensate for the differences in geometry and size between thedisc space and the pre-formed core.

[0065] Outer shell 30 is preferably resorbable and, in such form, ispreferably replaced with tissue, such as fibrous tissue and includingfibrous scar tissue, that may aid in permanently confining the loadbearing elastic body within the disc space. Referring now to FIGS. 3 and4, tissue 33 has replaced outer shell 30, and thus surrounds elasticbody 15. Although elastic body 15 may be confined within the disc spacewith the aid of tissue 33, body 15 is expected to have some mobility fornormal biomechanics.

[0066] The dimensions of load bearing elastic body 15 may vary dependingon the particular case, but elastic body 15 is typically sized forintroduction into an intervertebral disc space. Moreover, elastic body15 is preferably wide enough to support adjacent vertebrae and is of aheight sufficient to separate the adjacent vertebrae. In order toprovide long-term mechanical support to the intervertebral disc, thevolume of elastic body 15 in the disc space should be at least about50%, preferably at least about 70%, further preferably at least about80% and more preferably at least about 90% of the volume of the entiredisc space, the remaining volume occupied by outer shell 30. However,the volume of elastic body 15 may be as large as about 99% of the volumeof the intervertebral disc space, and thus about 99% of the volume ofimplant 10. Accordingly, the volume of outer shell 30 may be at leastabout 1% of the volume of the implant, but may range from about 1% toabout 50%. The appropriate size of implant 10 desired in a particularcase may be determined by distracting the disc space to a desired levelafter the desired portion of the natural nucleus pulposus and any freedisc fragments are removed, and measuring the volume of the distractedspace with an injectable saline balloon. The disc volume can also bemeasured directly by first filling the disc space with a known amount ofthe outer shell precursor material.

[0067] Elastic body 15 may be fabricated in a wide variety of shapes asdesired, as long as the body can withstand spinal loads and other spinalstresses. The non-degradable and preformed elastic body 15 may beshaped, for example, as a cylinder, or a rectangular block. The body mayfurther be annular-shaped. For example, implant 10′ in FIGS. 12 and 13has a spiral, or otherwise coiled, shape. The implant includes a firstend 23 and a second end 24. Elastic body 15 may also be shaped togenerally conform to the shape of the natural nucleus pulposus, or maybe shaped as further described below. Although elastic body 15 is shownas one piece in, for example, FIGS. 1-4, it may be made from one orseveral pieces.

[0068] Elastic body 15 may be formed from a wide variety ofbiocompatible polymeric materials, including elastic materials, such aselastomeric materials, hydrogels or other hydrophilic polymers, orcomposites thereof. Suitable elastomers include silicone, polyurethane,copolymers of silicone and polyurethane, polyolefins, such aspolyisobutylene and polyisoprene, neoprene, nitrile, vulcanized rubberand combinations thereof. The vulcanized rubber described herein may beproduced, for example, by a vulcanization process utilizing a copolymerproduced as described, for example, in U.S. Pat. No. 5,245,098 toSummers et al. from 1-hexene and 5-methyl-1,4-hexadiene. Suitablehydrogels include natural hydrogels, and those formed from polyvinylalcohol, acrylamides such as polyacrylic acid andpoly(acrylonitrile-acrylic acid), polyurethanes, polyethylene glycol,poly(N-vinyl-2-pyrrolidone), acrylates such as poly(2-hydroxy ethylmethacrylate) and copolymers of acrylates with N-vinyl pyrrolidone,N-vinyl lactams, acrylamide, polyurethanes and polyacrylonitrile, or maybe other similar materials that form a hydrogel. The hydrogel materialsmay further be cross-linked to provide further strength to the implant.Examples of polyurethanes include thermoplastic polyurethanes, aliphaticpolyurethanes, segmented polyurethanes, hydrophilic polyurethanes,polyether-urethane, polycarbonate-urethane and siliconepolyether-urethane. Other suitable hydrophilic polymers includenaturally-occurring materials such as glucomannan gel, hyaluronic acid,polysaccharides, such as cross-linked carboxyl-containingpolysaccharides, and combinations thereof. The nature of the materialsemployed to form the elastic body should be selected so the formedimplants have sufficient load bearing capacity. In preferredembodiments, a compressive strength of at least about 0.1 Mpa isdesired, although compressive strengths in the range of about 1 Mpa toabout 20 Mpa are more preferred.

[0069] Outer shell 30 may be formed from a wide variety ofbiocompatible, preferably elastic, elastomeric or deformable natural orsynthetic materials, especially materials that are compatible withelastic body 15. The outer shell materials preferably remain in anuncured, deformable, or otherwise configurable state during positioningof the elastic body in the interverterbral disc space, and shouldpreferably rapidly cure, become harder or preferably solidify afterbeing introduced into the intervertebral disc space, or, in otherembodiments, prior to positioning of the elastic body in theintervertebral disc space. In preferred embodiments, the outer shellmaterials may remain deformable after they harden or otherwise solidify.Suitable materials that may be used to form the outer shell includetissue sealants or adhesives made from natural or synthetic materials,including, for example, fibrin, albumin, collagen, elastin, silk andother proteins, polyethylene oxide, cyanoacrylate, polyarylate,polylactic acid, polyglycolic acid, polypropylene fumarate,tyrosine-based polycarbonate and combinations thereof. Other suitablematerials include demineralized bone matrix. These precursor materialsmay be supplied in liquid, solution or solid form, including gel form.

[0070] Elastic body 15 may include a variety of surface features onouter surface 16, including chemical modifications and surfaceconfigurations, to provide surface features that advantageously improvethe bonding between outer surface 16 of the elastic body and innersurface 32 of outer shell 30. In one form of the invention, outersurface 16 is chemically modified utilizing, for example, chemicalgroups that are compatible with the materials used to form outer shell30. Suitable chemical modifications include, for example, surfacegrafting of reactive functional groups, including hydroxyl, amino,carboxyl and organofunctional silane groups. The groups may be graftedby methods known to the skilled artisan. Other modifications includepre-coating with a primer, preferably one that is compatible with theouter shell material, such as a layer of adhesive, sealing or othermaterials used for forming the outer shell described above.

[0071] In yet another form of the invention, elastic body 15 may includea wide variety of surface configurations, such as macro-surfacepatterns, or protuberances, as seen in FIGS. 14A-14J, showing side viewsor top views of top portions of elastic bodies with various surfacefeatures. Referring now to FIGS. 14A-14J, the pattern may be a dove-tailpattern 200, a circular pattern 205, a square pattern 210, a conicalpattern 215, various wave patterns 220 and 225 and random, irregularpatterns 230. In other embodiments, a fiber 240 may be disposed inelastic body 241 and may project from the surface 242 thereof to form afibrous pattern 235. Fiber 240 may be disposed as a loop projecting fromthe surface of the elastic body, its ends may project from the surfaceof the elastic body, or the fiber may have a wide variety of otherappropriate configurations. The fiber may be a short, polymeric fiber,such as one that is cut to less than about one inch. The fiber may,alternatively, be a continuous polymeric fiber. The fiber may further bebraided, and may be woven or non-woven. The macro-surface patterns arepreferably formed during formation of elastic body 15. However, outersurface 16 of elastic body 15 may also be physically modified afterformation of elastic body 15 by, for example, laser drilling or thermaldeformation. Physical modifications include, for example, amicrotexturized surface formed by bead-blasting, plasma etching orchemical etching. Procedures for modifying various surfaces in thismanner are well known in the art.

[0072] In certain forms of the invention, the implant may include onlyelastic body 15 having one or more of the outer surface features asdescribed above, without the outer resorbable shell. The surfacefeatures are expected to provide a certain level of fixation to thesurrounding tissues for improved resistance to migration and/orexpulsion.

[0073] In yet other forms of the invention, the implant may include anelastic body that is surrounded by a supporting, or otherwiseconstraining, member wherein the supporting member is surrounded by aresorbable shell as described herein. Referring now to FIG. 5, implant400 includes a load bearing elastic body 15 that is surrounded by asupporting member 34. In one form, supporting member 34 may be apreferably flexible, peripheral supporting band that is disposedcircumferentially about elastic body 15 as seen in FIG. 5, leaving upperand lower surfaces 35 and 36, respectively, of elastic body 15 free fromthe supporting band.

[0074] As seen in FIG. 5, portions of upper and lower surfaces 35 and36, respectively, of elastic body 15 are exposed to directly contactouter shell 30. This exposure minimizes the amount of material needed toconstruct the supporting member, yet still effectively provides, forexample, lateral support. Although the amount of the upper and lowersurfaces of elastic body 15 that are exposed may vary, typically atleast about 50%, preferably at least about 70%, more preferably at leastabout 80% and most preferably at least about 90% of the surfaces areexposed.

[0075] In yet another embodiment shown in FIG. 6, nucleus pulposusimplant 500, that includes elastic body 15 as described above, isreinforced with supporting member 37, which takes the form of a jacket.The jacket preferably completely surrounds elastic body 15.

[0076] Suitable supporting members, including reinforcing outer bands,covers, or other jackets, may be formed from a wide variety ofbiocompatible polymers, metallic materials, or combination of materialsthat form a strong but flexible support to prevent excessivedeformation, including lateral (horizontal) deformation, of the coreunder increasing compressive loading. Suitable materials includenon-woven, woven, braided, or fabric materials made from polymericfibers including cellulose, polyethylene, polyester, polyvinyl alcohol,polyacrylonitrile, polyamide, polytetrafluorethylene, polyparaphenyleneterephthalamide, and combinations thereof. Other suitable materialsinclude non-reinforced or fiber-reinforced elastomers such as silicone,polyurethane, copolymers of silicone and polyurethane, polyolefins,including polyisobutylene and polyisoprene, neoprene, nitrile,vulcanized rubber, and combinations thereof. In a preferred form of theinvention, a combination, or blend, of silicone and polyurethane isused. Furthermore, the vulcanized rubber is preferably produced asdescribed above for the nucleus pulposus implants. Supporting members 34and 37 are advantageously made from a porous material, which, in thecase of an elastic body made from a hydrogel, or other hydrophilicmaterial, allows fluid circulation through the elastic core body toenhance pumping actions of the intervertebral disc. Supporting membersmay further be formed from carbon fiber yarns, ceramic fibers, metallicfibers or other similar fibers as described, for example, in U.S. Pat.No. 5,674,295.

[0077] FIGS. 7A-7D show supporting bands of various patterns, typicallymade from various braided materials (bands 25, 26 and 27), or porousmaterials (band 28), as described above. It is also understood thejackets may also be formed of such patterns. It is realized that thebraided materials may also be porous.

[0078] Supporting members 34 and 37 preferably decrease lateraldeformation, compared to deformation of an implant without thesupporting member, as desired. Supporting members 34 and/or 37 may, forexample, decrease lateral deformation by at least about 20%, preferablyat least about 40%, more preferably by at least about 60% and mostpreferably by at least about 80%. An implant, such as one that includesan elastic body, having such a supporting member will be flexible andotherwise resilient to allow the natural movements of the disc andprovides shock absorption capability at low to moderate applied stress,but will resist excessive deformation for disc height maintenance underhigh loading conditions. As described herein in the case of a lumbardisc, for example, low applied stress includes a force of about 100Newtons to about 250 Newtons moderate stress includes a force of about250 Newtons to about 700 Newtons, and high loading conditions, or highstress, includes a force of above about 700 Newtons. In preferred formsof the invention, the supporting member is flexible, in that it may befolded, or otherwise deformed, but is substantially inelastic, so thatthe implant is more fully reinforced or otherwise supported.

[0079] The elastic body may be covered by the jacket supporting member,or the band supporting member may be wrapped around the circumference ofthe elastic body. In a form of the invention wherein the elastic body isformed from a hydrogel, or similar hydrophilic material, the hydrogelmay be dehydrated a desired amount prior to being covered by the jacket,or prior to wrapping the band around the circumference of the hydrogelbody. The hydrogel elastic body may be exposed to saline outside of thebody, or may be inserted into the disc space wherein it will be exposedto body fluids in situ, and the body will absorb water and swell. Inreference to the peripheral band supporting member, the swelling orexpansion of the hydrogel elastic body in the horizontal direction iscontrolled by the amount of slack designed in the band. After thelimited allowable horizontal expansion is reached, the elastic body isforced to expand mostly in the vertical direction until reachingequilibrium swelling under the in vivo load. As the upper and lowersurfaces of the elastic body are not substantially constrained, thevertical expansion is mainly controlled by the applied stress and thebehavior of the hydrogel material.

[0080] In yet other forms of the invention, an implant reinforced with aperipheral supporting band as described above that is surrounded by aresorbable outer shell may be further reinforced with one or morestraps. The straps may be advantageous in preventing the peripheralsupporting band described herein from slipping, or otherwise sliding offthe implant. Referring now to FIGS. 8 and 9, at least one strap 420extends along upper surface 35 and at least one strap 430 extends alonglower surface 36 of elastic body 15 of implant 400. Ends 421 of strap420 and ends 431 of strap 430 are each preferably connected, orotherwise attached, to peripheral supporting band 34′. The point ofattachment may be any location that will secure the strap, including atthe upper margins 138 of the band, lower margins 139 of the band or anyregion between the upper and lower margins. Although two straps 420 and430 are shown extending along upper surface 35 and lower surface 36,respectively, in FIGS. 8 and 9, one continuous strap may be utilizedthat extends completely around the implant, or the strap utilized may bein one, two or multiple pieces, as long as the combination of straps aresufficient to prevent excessive slipping and or sliding of thesupporting band. Furthermore, more than one strap may extend along uppersurface 35 and more than one strap may extend along lower surface 36 ofelastic body 15, as seen, for example, in FIGS. 10 and 11 of implant500, wherein straps 520, 530, 540 and 550 are shown attached, orotherwise connect to supporting member 34″. It is realized that thestraps may be present in one or more pieces. For example, straps 520 and530 may form a single strap, as may straps 540 and 550, or may allcombine to form a single strap.

[0081] In other aspects of the invention, kits designed for forming theintervertebral disc nucleus pulposus implants that include the outershell described above are provided. In one form, a kit may include aload bearing elastic body as described above, along with a container ofmaterial to form the outer, preferably resorbable, shell. The materialmay be selected from the materials as described above. Moreover, thecontainer that houses the material that forms the shell may be made froma wide variety of materials that are compatible with the outer shellmaterial, including glass and plastic. The kit may further include asupporting member, such as a supporting band, jacket or other outercover as described above. Generally, the kits include sterile packagingwhich secures the kit components in spaced relation from one anothersufficient to prevent damage of the components during handling of thekit. For example, one may utilize molded plastic articles known in theart having multiple compartments, or other areas for holding the kitcomponents in spaced relation.

[0082] In a further aspect of the invention, nucleus pulposus implantsare provided having shape memory that are configured to allow extensiveshort-term manual, or other, deformation without permanent deformation,cracks, tears, breakage or other damage, that may occur, for example,during placement of the implant into an intervertebral disc space.Referring now to FIGS. 15A and 16A, in one form of the invention,implant 40 includes a load bearing elastic body 41 with shape memory andhaving a first end 42 and a second end 43 that are positioned adjacentto a central portion 44 to form at least one inner fold 45. Inner fold45 preferably defines at least one aperture 46 which is advantageouslyarcuate. The elastic body is deformable, or otherwise configurable,manually, for example, from this first folded, or otherwise relaxedconfiguration shown in FIG. 15A into a second, substantiallystraightened, or otherwise non-relaxed configuration shown in FIG. 16Afor placement into the intervertebral disc space. As elastic body 41 hasshape memory, it returns by itself, automatically, back into the firstfolded, relaxed configuration once manual or other force is no longerexerted on the body. These implants therefore provide improved handlingand manipulation characteristics in that they may be deformed,configured and otherwise handled by an individual without resulting inany breakage or other damage to the implant.

[0083] Further describing the shape memory nucleus prosthesis implant40, implant 40 includes surface depressions 47, or other surfaceirregularities as more fully described below, that form inner fold 45when the implant is in its relaxed configuration. Ends 42 and 43 haveend surfaces 42 a and 43 a, respectively, that are generally flat, andsubstantially parallel, or perpendicular in other forms, to an axis Xpassing through the width of the implant in its relaxed configuration,wherein the ends may abut each other as seen in FIGS. 15A, 15B and15E-15N. The ends of the implant may each alternatively abut the centralportion of the implant, as shown for implants 60 and 70 in FIGS. 15C and15D, respectively, to form a generally bi-lobed or binocular-shapedimplant.

[0084] Alternatively, in other forms of the invention, one end of theimplant may be tapered, or otherwise specifically shaped, and the otherend may be shaped complementary to the tapered, or otherwise shaped,end. Moreover, either one or both sides 96 a and 96 b of the ends of thenucleus pulposus implant may be tapered. For example, and as seen inFIGS. 15F and 16F, both sides of end 93 of implant 90 are tapered toform a pointed end, such as a generally V-shaped end, thatadvantageously fits into a complementary-shaped (e.g., V-shaped)depression 95 defined by end 92. An implant having only one inner foldthat defines one aperture and ends that are similarly configured as ends92 and 93 is shown in FIGS. 15J and 16J. As another example, one side ofeach of the ends of the implant may be oppositely tapered as seen inFIGS. 15G and 16G. That is, side 108 a of end 102 of implant 100 andopposite side 109 b of end 103 are tapered as seen in FIG. 15G and 16G.End surfaces 102 a and 102 b of implant 100 are transverse to axis Xwhen the implant is in its relaxed configuration shown in FIG. 15G. Inthose embodiments where the ends of the implants are tapered, orotherwise shaped, it is preferred that, when the ends of the implantscontact each other or the central or other portion of the implant, animplant is formed that is uniform along the length of the implantthrough the region of contact.

[0085] Although the implant may assume a wide variety of shapes, it istypically shaped, in its folded, relaxed configuration, to conform tothe shape of the natural nucleus pulposus. Thus, the implants may besubstantially elliptical when in their folded, relaxed, configurationsin some forms of the invention. In yet further forms of the invention,the shape of the implants in their folded configurations may begenerally annular-shaped or otherwise shaped as required to conform tothe intervertebral disc cavity. Moreover, when the implants are in theirunfolded, non-relaxed, configuration, such as their substantiallystraightened configuration, they may also assume a wide variety ofshapes, but are most preferably generally elongated, and preferablygenerally cylindrical, or other shape as described herein.

[0086] In yet other forms of the invention, the folding implant may havea surface that includes surface projections that further aid in allowingshort-term deformation of the implant without permanent deformation orother damage as described above. Referring now to FIGS. 15D and 16D,implant 70 includes a load bearing elastic body 71 having a first end72, a second end 73 and a central portion 74. Inner fold 75 defines anaperture 76 and includes an inner fold surface 77 having wrinkles, orprojections 78 thereon. Projections 78 of inner fold surface 77 extendinto aperture 76. These wrinkles advantageously facilitate stretching ofthe implant without deformation, cracking, tearing, breakage, or otherdamage when the implant is straightened or elongated for insertion intothe intervertebral disc space. In the embodiment shown in FIGS. 15D and16D, the wrinkles, or surface projections, extend along the entirelength of elastic body 71, including central portion 74. Other implantshaving wrinkled inner fold surfaces are seen in FIGS. 15E and 16E andother wrinkle configurations upon folding the implant are seen in FIGS.15K-15N and 16K-16N.

[0087] Other folding implants are shown in FIGS. 22A-22Q, 23A-23Q and24-27. Referring to these figures, implants 400-620 are shown that havea plurality of inner folds, ranging from, for example, two to about six.Moreover, these implants, as well as the above-discussed foldingimplants, have first and second ends that are formed from first andsecond arms, respectively, of the implants. As seen in FIGS. 22A and23A, for example, first end 402 of implant 400 is formed from a firstarm 408 connected to, or otherwise associated with, one end 404 a ofcentral portion 404. Second end 403 is formed from a second arm 409connected to, or otherwise associated with, opposing end 404 b ofcentral portion 404. Surface depressions 405 or other surfaceirregularities define inner folds 406 when the implant is in its relaxedconfiguration.

[0088] In certain forms of the invention, each of the arms connected tothe central portions of the implant are the same length, as seen inFIGS. 15A-15J, 15L-15N, 22A-22B, 23A-23B, 22D-22E, 23D-23E, 22G and 23G.In yet other forms of the invention, one of the arms is shorter than theother arm. For example, as seen in FIG. 22C, second arm 429 of implant420 is shorter than first arm 428, wherein each arm is connected to anend of central portion 424. Stated alternatively, in certain forms ofthe invention, the ends of the implant abut each other along a planeextending along axis X and passing through the width of the implant,resulting in a center or central closure C of the implant as seen, forexample, in FIG. 22A. In other forms of the invention, the ends of theimplant abut each other along a plane extending parallel to a planeextending along axis X and passing through the width of the implant,resulting in an off-center closure C′ of the implant as seen, forexample, in FIG. 22C. The differential length of the arms of theimplants can facilitate implantation and proper positioning of theimplants in the disc space as more fully described below.

[0089] Moreover, some of the inner folds of the implants may be formedwhen the first end and the second end of the implant contact, orotherwise abut, each other, as seen, for example, in FIG. 22C. In suchforms of the invention, each end of the implant may include a surfacethat has a surface depression, such as surface depression 421 or 422, asseen in FIG. 23C, that forms a portion of the inner fold such that whenthe ends of the implant contact each other, an inner fold is formed fromthe combination of surface depressions. Additionally, the aperturesdefined by the inner folds may have a variety of cross-sectional shapes,including substantially annular or otherwise ring-shaped, substantiallyoval or otherwise elliptical-shaped, star-shaped or other various shapesknown to the skilled artisan. The star-shaped pattern includes aplurality of finger-like or otherwise elongated projections 465 or 475as seen, for example, in FIGS. 22G and 22H, respectively.

[0090]FIGS. 221, 231, 24, 22K, 23K and 26 show further details ofimplants of the present invention. For example, apertures, or channels,486 and 506, can be seen in FIGS. 24 and 26, respectively, showingimplants 480 and 500, respectively. Turning now to FIGS. 22J, 23J and25, implant 490 is shown that includes all of the features of theaforementioned implants, including a load bearing body 491, a first arm498 having a first end 492, a second arm 499 having a second end 493,and surface depressions 497. Additionally, implant 490 includes acentral portion 494 that extends along the full width of implant 490from one end of the implant to an opposing edge of the implant. In suchan embodiment, end surfaces 492 a and 493 a abut, and are otherwise incontact with, central portion 494 when implant 490 is in its foldedconfiguration as seen in FIG. 22J.

[0091] In one form of the invention, at least one end of the implantsmay be curved, or otherwise arcuately-shaped or rounded. Referring toimplant 510 in FIGS. 22L and 23L, first end 512 and second end 513 eachhave an inner edge 512 b and 513 b, and an outer edge, 512 a and 513 a,respectively. Outer edges 512 a and 513 a are shown as rounded and canfacilitate implantation and proper positioning of the implants in thedisc space as more fully described below.

[0092] For example, the rounded edges allow for better conformity of theimplant to the disc space. Although not being limited by theory, it isbelieved that the dome-shaped, or otherwise concave-shaped, endplatesmay lead to increased stress concentrated at the edges of the implant.The rounded edges reduce such stress. In this manner, there is a smallerlikelihood of the implant penetrating the endplate, and the durabilityof the implant is improved. Bone remodeling based on the shape of theimplant is also reduced.

[0093] Referring to FIGS. 22M and 23M, implant 610 is shown wherein bothends of the implants have edges that are curved or otherwise rounded.Implant 610 includes body 611 having first arm 613 and second arm 614.First arm 613 and second arm 614 include ends 613 a and 614 a,respectively, which both preferably have rounded edges 613 b and 614 b,respectively, although only one of the ends may have such a rounded,straight or other shaped edge. In this embodiment, end 614 a of secondarm 614 is tapered, or otherwise has a decreased diameter compared toend 613 a of first arm 613. Additionally, first arm 613 is shorter thansecond arm 614.

[0094] Referring to FIGS. 22N-22Q, 23N-23Q and FIG. 27, alternativeembodiments of the above-described folding implants are shown. As withall of the implants, the bodies forming the implants have a top surfaceT for contacting an upper vertebral endplate of an intervertebral discand a bottom surface B for contacting a lower vertebral endplate of theintervertebral disc as seen, for example, in FIG. 27. Additionally, theimplants have an external side surface E that includes at least onegroove G extending along the side surface that advantageously furtherrelieves the compressive force on the external side E of the implantwhen the implant is deformed into a substantially straightened, orotherwise unfolded configuration and thus further allows extensiveshort-term deformation without permanent deformation, cracks, tears orother breakage. For example, implant 620 shown in FIGS. 22N, 23N and 27includes a load bearing body 621 that has a top surface T, a bottomsurface B, an internal side surface I and an external side surface E. Aplurality of grooves G are disposed along external side surface E thattypically extend from the top surface to the bottom surface of theimplant. When dividing the implant in half, thus more easily viewing afirst side S₁ and a second side S₂, with a plane passing through thewidth of the implant along axis X, it can be seen in FIG. 22N that fourgrooves G are present on first side S₁ and four grooves G are present onsecond side S₂, although more or less may be present depending on thecase. It is preferred that at least one groove is present on each sideS₁ and S₂.

[0095]FIGS. 220 and 230 depict implant 570, which is similar to implant620, with the exception that implant 570 includes a second arm 572 thatis smaller than first arm 571, resulting in an off-center closure C′ asmore fully described above. FIGS. 22P and 23P depict implant 610′ andFIGS. 22Q and 23Q depict implant 490′, which are identical to implants610 and 490, respectively, with the exception that implants 490′ and600′ both include external side grooves G as described herein.

[0096] In yet other preferred forms of the invention, the top and bottomcontact surfaces of the implants are configured to be complementary tothe top and bottom endplates of an intervertebral disc, respectively.For example, the top and bottom contact surfaces of the implants may beconvex, to conform to the respective concave intervertebral discendplates. Additionally, although the implants are preferably one-pieceimplants, they may also be composed of one or more pieces. For example,an implant may be composed of a separate central portion and first andsecond arms, wherein the arms are associated or otherwise attached tothe central portion as described herein.

[0097] In certain preferred forms of the invention, the aperturesdefined by the inner folds of the implants described above have a radiusof at least about 1 mm. Moreover, in other preferred forms of theinvention, a reinforcing material may be included at the inner foldsurface to further improve the structural integrity of the implant. Thereinforcing material may be a fabric that is either woven, or non-woven,and may be formed from braided fibers for further strength. Thereinforcing material may be positioned on the inner fold surface, mayproject therefrom or may be entirely embedded under the inner foldsurface. The implant may be formed as a single piece, or may be formedof more than one piece that is connected to the other pieces that formthe assembled implant by fabric that may be made from braided or otherfibers, or may be connected by some other components or manner, such asby use of adhesives, or other methods of connecting such componentstogether. Although these implants are designed to be used without ananchoring outer shell, they, as well as all of the implants describedherein, may form the core elastic body of an implant that includes theouter shell described herein.

[0098] The implants may obtain their shape memory characteristics in avariety of ways. For example, the implants may be formed in a mold intoa desired final shape, and, when deformed from this final shape byapplication of an external force, will return to the final shape uponrelease of the force.

[0099] In yet another embodiment of the invention, a nucleus pulposusimplant is provided that has a locking feature, with optional shapememory characteristics, and thus may also resist being expelled from thedisc cavity to some extent. In one form of the invention as seen inFIGS. 17-19, an implant 300 includes a load bearing elastic body 301having a first end 302 and a second end 303. The ends are typicallyconfigured for mating engagement with each other. Elastic body 301 has afirst, locked configuration wherein first end 302 and second end 303 arematingly engaged to each other as seen more particularly in FIG. 17.When elastic body 301 has shape memory characteristics, elastic body 301is deformable, manually, for example, into a second, substantiallystraightened, non-relaxed configuration for insertion into anintervertebral disc space, as seen in FIG. 19, and may automatically beconfigured or otherwise returned back into the first, locked, relaxedconfiguration after insertion due to its shape memory characteristics.In those cases where the elastic body does not have shape memorycharacteristics and the elastic body is configurable into a lockedand/or straightened configuration, and in those cases where the elasticbody has shape memory characteristics, the elastic body may also beplaced into its locked configuration with the assistance of externalforce.

[0100] More particularly describing one form of the invention, end 302defines an internal channel 304 as seen in FIG. 19 whereas end 303 isconfigured to conform to the shape of internal channel 304. The channelmay take the form of a wide variety of shapes, as long as the ends ofthe elastic body may be matingly engaged to form a locked configuration.As seen in FIG. 19, the channel is somewhat hour-glass shaped. Manual,or other force, may be applied to end 303 so that it may be temporarilydeformed, or configured, sufficiently to pass through narrowed passage305 within internal channel 304. Once properly positioned, end 303 willbe secured within channel 304, as end edges 303 a and 303 b are bracedagainst channel edges 304 a and 304 b, respectively. Alternatively, oneend of an implant with a locking feature may be friction-fit within theinternal channel present in the other end of the implant. Thefriction-fit may arise as a result of the relative size differencesbetween the inner diameter of the channel formed by one end and theouter diameter of the other end of the implant. Additionally, and/oralternatively, the outer surface of one end, and/or the inner surface ofthe channel defined by the other end, may include surface roughenings asdescribed herein that aid in achieving the friction-fit. The implant mayalso be constructed from the biocompatible polymeric materials asdescribed above.

[0101] When the implants are formed from an elastic material, such as ahydrogel, or other similar hydrophilic material, or include theresorbable outer shell, they may advantageously deliver desiredpharmacological agents. The pharmacological agent may be a growth factorthat may advantageously repair the endplates and/or the annulusfibrosis. For example, the growth factor may include a bonemorphogenetic protein, transforming growth factory-β (TGF-β),insulin-like growth factor, platelet-derived growth factor, fibroblastgrowth factor or other similar growth factor or combination thereofhaving the ability to repair the endplates and/or the annulus fibrosisof an intervertebral disc.

[0102] The growth factors are typically included in the implants intherapeutically effective amounts. For example, the growth factors maybe included in the implants in amounts effective in repairing anintervertebral disc, including repairing the endplates and the annulusfibrosis. Such amounts will depend on the specific case, and may thus bedetermined by the skilled artisan, but such amounts may typicallyinclude less than about 1% by weight of the growth factor. The growthfactors may be purchased commercially or may be produced by methodsknown to the art. For example, the growth factors may be produced byrecombinant DNA technology, and may preferably be derived from humans.As an example, recombinant human bone morphogenetic proteins (rhBMPs),including rhBMP 2-14, and especially rhBMP-2, rhBMP-7, rhBMP-12,rhBMP-13, and heterodimers thereof may be used. However, any bonemorphogenetic protein is contemplated including bone morphogeneticproteins designated as BMP-1 through BMP-18.

[0103] BMPs are available from Genetics Institute, Inc., Cambridge,Mass. and may also be prepared by one skilled in the art as described inU.S. Pat. No. 5,187,076 to Wozney et al.; U.S. Pat. No. 5,366,875 toWozney et al.; U.S. Pat. No. 4,877,864 to Wang et al.; U.S. Pat. No.5,108,922 to Wang et al.; U.S. Pat. No. 5,116,738 to Wang et al.; U.S.Pat. No. 5,013,649 to Wang et al.; U.S. Pat. No. 5,106,748 to Wozney etal.; and PCT Pat. Nos. W093/00432 to Wozney et al.; W094/26893 toCeleste et al.; and W094/26892 to Celeste et al. All bone morphogenicproteins are contemplated whether obtained as above or isolated frombone. Methods for isolating bone morphogenetic protein from bone aredescribed, for example, in U.S. Pat. No. 4,294,753 to Urist and Urist etal., 81 PNAS 371, 1984.

[0104] In other forms of the invention, the pharmacological agent may beone used for treating various spinal conditions, including degenerativedisc disease, spinal arthritis, spinal infection, spinal tumor andosteoporosis. Such agents include antibiotics, analgesics,anti-inflammatory drugs, including steroids, and combinations thereof.Other such agents are well known to the skilled artisan. These agentsare also used in therapeutically effective amounts. Such amounts may bedetermined by the skilled artisan depending on the specific case.

[0105] The pharmacological agents are preferably dispersed within thehydrogel, or other hydrophilic, implant for in vivo release, and/or,with respect to the implants with the resorbable outer shell, may bedispersed in the outer shell. The hydrogel can be cross-linkedchemically, physically, or by a combination thereof, in order to achievethe appropriate level of porosity to release the pharmacological agentsat a desired rate. The agents may be released upon cyclic loading, and,in the case of implants including a resorbable outer shell, uponresorption of the shell. The pharmacological agents may be dispersed inthe implants by adding the agents to the solution used to form theimplant, by soaking the formed implant in an appropriate solutioncontaining the agent, or by other appropriate methods known to theskilled artisan. In other forms of the invention, the pharmacologicalagents may be chemically or otherwise associated with the implant. Forexample, the agents may be chemically attached to the outer surface ofthe implant.

[0106] The implants described herein may have embedded therein smallmetal beads or wire for x-ray identification.

[0107] Methods of forming and implanting the nucleus pulposus implantsdescribed herein are also provided. In one form of the invention, withrespect to implant 10 described above having the anchorable outer shell30, implant 10 may be formed by first forming elastic body 15 and thenforming the outer shell. Methods of forming elastic body 15 are wellknown in the art.

[0108] For example, if the elastic body is made of elastomericmaterials, such as powdered elastomers including, for example,styrene-ethylene/butylene block copolymers, the powdered elastomer maybe placed into an appropriate mold and may be compressed and heated tomelt the powder. The mold is then cooled to room temperature. If theelastic body is made from a hydrogel, such as a polyvinyl alcohol, thepolyvinyl alcohol powder may be mixed with a solvent, such as, forexample, water or dimethylsulfoxide, or combinations thereof, and heatedand shaken until a uniform solution is formed. The solution may then bepoured into a mold, such as a rubber mold, and may be cooled at anappropriate temperature, such as about 0° C. to about −80° C., forseveral hours to allow for crystallization. After cooling, the hydrogelcan be partially or completely hydrated by soaking and rinsing withwater but, in certain preferred embodiments, may remain dehydrated sothat it may be inserted through a smaller aperture in the annulusfibrosis.

[0109] Prior to positioning the implant in the interverterbral discspace, an incision may be made in the annulus fibrosis, or one may takeadvantage of a defect in the annulus, in order to remove the naturalnucleus pulposus and any free disc fragments within the intervertebraldisc space. The disc space is then distracted to a desired level bydistractors or other devices known to the skilled artisan for suchpurposes. Once formed, and after preparing the disc space for receivingthe implant, elastic body 15 may be implanted into the intervertebraldisc space utilizing devices well known in the art and as described inU.S. Pat. Nos. 5,800,549 and 5,716,416. If the outer shell precursormaterial was already placed in the intervertebral disc space, excessprecursor material may flow out of the disc space. This excess materialshould be promptly removed before it sets or otherwise cures. The outershell material may be injected, or otherwise introduced, into the discspace utilizing devices that are well known in the art, such assyringes, sealant/caulk guns, automatic liquid injectors, andapplicators that include, for example, two separate syringes which allowfor simultaneous mixing of the components in a static mixer and deliveryto the site, and may be injected either prior to or after introductionof the implant into the disc space. Whether the outer shell material isintroduced prior to or after introduction of the implant into the discspace, the distractor is then removed, any excess precursor materialseeping out of the disc space is removed and the precursor materialwithin the disc space is cured to form the outer shell. It is noted thatthe elastic body may already be surrounded by the outer shell, which maybe in a partially or fully hardened state but preferably remainsdeformable, prior to introducing the elastic body into theintervertebral disc space.

[0110] In further aspects of the invention, spinal disc implant deliverydevices, or tools, are provided to be used in preferred methods ofimplanting the implants described herein, especially the shape memoryimplants. In one form, the device preferably includes an elongatedmember having a lumen extending longitudinally therethrough for loadingof the desired implant, a tip portion for controlling passage of theimplant out of the delivery tool and a plunger or other elongated memberor other device for pushing the implant through the tool and into anintervertebral disc cavity. The tip portion preferably includes amovable member that may be moved from a first, closed position in whichit blocks the passage of a spinal disc implant through the lumen, andout of the distal end, of the elongated member into which the spinalimplant is loaded and otherwise housed. The tip portion may alsopreferably be moved to a second, open position, wherein egress of thespinal implant is allowed.

[0111] Referring to FIG. 28, device 700 includes an elongated member701, such as a syringe housing 702 or other elongated housing or barrelthat defines a cavity, or lumen, 703 that extends along its length, andhas a proximal end 704 and a distal end 705. Proximal end 704 defines aflange 704 a. Inner surface 703 a of cavity, or lumen, 703 is preferablyconfigured for passage of a spinal nucleus pulposus implant. Forexample, inner surface 703 a is preferably smooth. Although elongatedhousing member 701 is shown in FIG. 29 as having a squarecross-sectional shape, the cross-sectional shape of housing member 701may vary along its length and may be selected from a wide variety ofgeometric shapes, including elliptical, circular, rectangular, hexagonalor other multi-sided shape or a combination thereof. Device 700 furtherincludes a plunger 706, or elongated or other member. Plunger 706includes an elongated member, or rod, 720 having proximal end 707 anddistal end 709 that may be utilized to push a nucleus pulposus implantthat may be disposed in cavity 703 through the housing and ultimatelyinto an intervertebral disc space. Distal end 709 of plunger 706 mayinclude a plunger tip 721 that is configured to contact an implantduring extrusion. The cross-sectional shape of plunger tip 721 ispreferably similar to that of elongated housing member 701. Proximal end707 of plunger 706 includes a plunger handle 722. Plunger 706 mayinclude one or more components that may facilitate extrusion of theimplant by pneumatic, hydraulic or mechanical force, or by manualpushing or impacted force. For example, the plunger can be in the formof a pushing or impacted plunger, a syringe plunger, a caulk gunplunger, or a screw-driven plunger as known in the art.

[0112] Device 700 further includes component, or tip portion, 710 havinga proximal end 713 and a distal end 712 wherein tip portion 710 may beintegral or detachable. For example, proximal end 713 of tip portion 710may be matingly engageable to, or is otherwise connected or associatedwith, distal end 705 of housing 702 of member 701. In one form of theinvention depicted in FIG. 29, tip portion 710 may include a top wall730, a bottom wall 735, a side wall 740 and an opposing side wall 745.Tip portion 710 defines a cavity, or lumen, 731 extending longitudinallytherethrough wherein lumen 731 is continuous, and otherwise in fluidcommunication, with lumen 703 of elongated housing member 701.

[0113] The dimensions of tip portion 710, such as height H and width W,may be configured to accommodate a spinal disc implant to be delivered.Height H of tip portion 710 may have a height similar to or larger thanthe disc space height depending on whether disc space distraction isrequired. Additionally, length L of the tip portion may be chosen sothat tip portion 710 will preferably not substantially extend past theinner wall of the annulus fibrosis as described more fully below.Different dimensions of the tip portion may be determined by the skilledartisan.

[0114] Tip portion 710 is preferably configured to enter an aperture inan annulus fibrosis for delivery of a spinal nucleus pulposus implant orother spinal implant. Although tip portion 710 is shown as a rectangulartube in FIG. 29, it may have a wide variety of shapes, includingcylindrical, square, hexagonal or other multi-sided shape. Surface 732of top wall 730 and surface 733 of bottom wall 735 contact the endplatesduring delivery of the implant, and may have surface features 738 thathelp anchor, engage or otherwise secure the tip to the opposingendplates. Examples of such surface features, such as surfaceroughenings, are shown in FIGS. 30A-30J and include teeth 738 c-738 g,in the form of serrations or spikes (FIGS. 30C-30H), ridges 738 i and738 j (FIGS. 30I and 30J) a textured surface 738 b (FIG. 30B) or anon-textured surface 738 a (FIG. 30A). The teeth or ridges may bedirectional and may restrict movement in a single direction, as seen inFIGS. 30D, 30E, 30F, and 30G for example.

[0115] In yet another form of the invention, one side wall may beshorter than the other to aid delivery and placement of the spinal discimplants described herein. Referring to FIG. 31, delivery device 700 aincludes tip portion 710 a having side wall 740 a that is shorter thanside wall 745 a. FIG. 32 shows one way in which delivery of an implant40 is aided. For example, as implant 40 exits the device, it veers tothe shorter side wall and will subsequently fold up in the disc space.

[0116] In a further form of the invention, the top and bottom walls ofthe tip portion may be partially open to alleviate any possibleconstriction of the implant as it exits the device and is delivered intoa disc space. For example, referring to FIG. 33, tip portion 710′ ofdevice 700′ may include a top wall 730′ having an opening 739 and abottom wall 735′ having an opening 741, wherein both openings may extendfrom a proximal end 712′ to a distal end 713′ of tip portion 710′. Insuch a fashion, tip portion 710′ forms opposing arms 736 and 737, eachhaving an inner surface I and an outer surface O. Inner surfaces I arepreferably concave and preferably accommodate a spinal disc implant.

[0117] Although both arms 736 and 737 of tip portion 710′ are shown inFIG. 33 as having the same length, one of the arms may be shorter thanthe other to, for example, aid placement of the folding implantsdescribed herein. For example, as seen in FIG. 34, arm 736′ of tipportion 710″ of device 700″ is shorter than arm 737″.

[0118] In yet another embodiment of a spinal disc implant deliverydevice, one of the arms of the tip portion may be movable and the othernon-movable or otherwise stationary. As seen in FIG. 35, for example,arm 737″ of tip portion 710′″ of device 700′″ is similar inconfiguration as arm 737′ and is preferably non-movable and furtherpreferably otherwise rigid. Arm 736″ may also be non-movable orotherwise rigid, but it may include both a non-movable portion 736 a″and a movable, flexible or otherwise elastic portion 736 b″ so that arm736″ may move, or be bent, and form a closed configuration. For example,by appropriately positioning arm portion 736 b″, arm 736″ may be bent,preferably at an angle a of greater than about 30°, further preferablybetween about 45° to about 90°, and typically about 60°. It ispreferred, especially when the tip portion also functions as adistractor, that the movable portion of the arm has a height that isless than the height of a disc space, and/or the height of the arm atits distal end is shorter than at its proximal end, so that it may movefreely. In the closed configuration, the width W of distal end 713′″ oftip portion 710′″ is narrow, such as about 2 mm to about 10 mm, whichmakes it easier to guide the tip portion into a small annular opening.Additionally, the implant for delivery will be blocked from exiting thedelivery device by arm 736″ in its closed configuration.

[0119] After the tip portion is inserted into the disc space, movablearm 736″ may be moved, radially, for example, to form an openconfiguration, such as the configuration of arm 736 of device 700′ ofFIG. 33, under extrusion pressure to expand the annular opening and toallow the implant to exit the device and enter the disc space asdescribed below. After the implant is delivered to the disc space, themovable arm retracts, bends or otherwise moves back to its closedconfiguration in order to decrease the expansion of the annular opening.It is realized that both arms may also be rigid, flexible or otherwiseelastic as desired. Other tip portions that have such open and closedconfigurations are described below. In preferred embodiments of thespinal disc implant delivery devices described herein, the tip portionhas wall support for the top, bottom and side surfaces of the spinaldisc implants to be delivered. It is further noted that lumens 703′,703″, 703′″ of elongated members 701′, 701″ and 701′″, respectively, arecontinuous, and in fluid communication, with cavity 731′, 731″, 731′″,respectively.

[0120] In yet another form of the invention, and referring to FIG. 36, aspinal disc implant delivery device 800 includes an elongated member801, such as a syringe housing 802 that defines a cavity 803, and has aproximal end 804 with a flange portion 804 a and a distal end 805.Device 800 further includes a plunger 806, or elongated or other member,having proximal end 807 and distal end 809 that may be utilized to pusha nucleus pulposus implant that may be disposed in cavity 803 throughthe housing, out of the distal end of the housing and ultimately into anintervertebral disc space.

[0121] Device 800 further includes component, or tip portion, 810 havinga proximal end 813 and a distal end 812, wherein proximal end 813 ismatingly engageable to, or is otherwise connected or associated with,distal end 805 of housing 802 of member 801 which is also seen in FIG.36. Tip portion 810 preferably includes a base member 850 which has aproximal end 851, a distal end 852, and a lumen 853 extendinglongitudinally therethrough. Tip portion 810 further preferably includesat least one movable member that may form a closed configuration asdescribed herein. In preferred forms of the invention, tip portion 810includes a plurality of movable members 880. Proximal end 881 of movablemembers 880 abut, or are connected to or are otherwise associated with,distal end 852 of base member 850.

[0122] Movable members 880 have a first, closed configuration whereinthey define a channel or cavity 883. The members may further have aclosed configuration which includes a narrowed distal end. Lumen 853 ofbase member 850 and cavity 883 are preferably in fluid communication.Lumen 853 of base member 850 and cavity 803 of housing 802 are alsopreferably in fluid communication when distal end 805 of housing 802 andproximal end 851 of base member 850 are matingly engaged. In theirclosed configuration, movable members 880 preferably further define anaperture 884, or other opening, at their distal end as best seen in FIG.37A. Aperture 884 is preferably sized and/or configured for ease ofinsertion of the tip into an annular opening, preferably an undersizedor relatively small annular opening. For example, the diameter ofaperture 884 of movable members 880 may range from about 2 mm to about10 mm in its closed configuration.

[0123] Movable members 880 are preferably movable, flexible, orotherwise elastic, but in certain forms of the invention may beotherwise rigid, and further have an open configuration wherein movablemembers 880 are moved, flexed or otherwise bent sufficiently to enablepassage of a spinal implant, such as a nucleus pulposus implantdescribed herein, through lumen 853 of base member 850 and through anarea circumscribed by the movable members in their open configuration sothat the spinal implant may exit the delivery tool and may be insertedinto or otherwise positioned in an intervertebral disc space. Movablemembers 880 are preferably placed in their open configuration when, forexample, a spinal implant is positioned in housing 802 of syringe 801and plunger 806, or other elongated or similar member, transmits a forcesufficient for translation of the spinal implant through cavity 803 ofhousing 802, lumen 853 of base member 850 and cavity 884 defined bymovable members 880. Contact of the inner surfaces of movable members880 with, and continued translation of, a spinal implant toward distalend 812 of device 800 forces the radial flexing, bending or movement ofmovable members 880 as more fully described below.

[0124] Movable members 880 and base member 850 may be engaged, connectedor otherwise associated with each other in a variety of ways, includinguse of an adhesive. Moreover, movable members 880 and base member 850may be integral. Base member 850 may also be integral with syringehousing 802, or may be attached by adhesive or other manner ofattachment described herein and/or known to the skilled artisan. Forexample, base member 850 may have an inner surface 854 defining lumen853 that is tapered as desired to varying degrees so that base member850 may be associated with syringe housing 802 by friction fit. Othermechanical interlocking methods known to the art may also be utilized tocouple proximal end 851 of base member 850 to distal end 805 of housing802 of syringe 801.

[0125] Tip portion 810 may include a plurality of movable members andmay assume a wide variety of shapes. As seen in FIG. 37A, tip portion810 is round and includes 16 movable members 880, although more or lessmay be present as desired. For example, the tip portion may include 8movable members 780 b, 780 c and 780 d (tip portion 810 b-810 d,respectively) as seen in FIGS. 37B-37D, 4 movable members 780 e (tipportion 810 e) as seen in FIG. 37E or 2 movable members 780 f (tipportion 810 f) as seen in FIG. 37F. Additionally, the movable membersmay contact a neighboring movable member or may be variously spacedapart. For example, FIGS. 37D, 37E and 37F show movable members, some ofwhich are spaced apart by space S. Furthermore, the tip portions mayassume a wide variety of cross-sectional shapes, including circular,elliptical, square, rectangular or other multi-sided or geometric shape.

[0126] The housing members, plunger members and base members describedherein may be made from a variety of materials, including metals knownto the art, such as stainless steel and titanium alloys, polymers knownto the art, including polyethylene, polypropylene, polyetheretherketoneand polyacetal. Movable members, such as movable members 880, may alsobe made from a variety of materials, preferably those which are flexibleor otherwise elastic, and allow for flexing, bending or pivoting.Movable members 880 may be made from the same materials as the housingmembers, plunger members and base members described herein.

[0127] In yet another form of the invention, a method for implanting aprosthetic intervertebral disc having shape memory is provided. In oneembodiment, an implant including a load bearing elastic body having afirst end and a second end positioned adjacent to a central portion toform at least one inner fold as described above is provided. Asmentioned previously herein, the disc space may be distracted ifnecessary and all or a portion of the nucleus pulposus may be removed.The implant 40, for example, may be deformed by, for example, manualforce into a substantially straightened, non-relaxed configuration forinsertion through an aperture formed in the annular fibrosis asindicated in FIG. 20, and as best seen in FIG. 21. The aperture may beformed through deterioration or other injury to the annulus fibrosis, ormay be made by purposely incising the annulus. The implant may then bepositioned in a delivery tool 310 known in the art, such as thatdescribed in U.S. Pat. No. 5,716,416, and inserted through aperture 18in annulus 19, although utilization of the delivery devices or toolsdescribed more fully herein is preferred. As the implant enters theintervertebral space 20 and is no longer subject to manual force, itdeforms back into its relaxed, folded configuration as seen in FIG. 21.A portion, or substantially all, of the natural nucleus pulposus may beremoved from the intervertebral disc space, depending on thecircumstances, prior to introduction of the implant into theintervertebral disc space. When implanting an implant that includes alocking feature, or other implant with shape memory as described herein,a similar protocol is followed. Additionally, with respect to an implantwith a locking feature, the implant may be placed into the lockedconfiguration with external force, imposed by, for example, medicalpersonnel. It is noted that, due to the symmetrical features of avariety of the implants described herein, the implant may be insertedinto the disc space by a wide variety of approaches, including anteriorand posterior approaches.

[0128] In preferred forms of the invention, a method for implanting aprosthetic intervertebral disc having shape memory is practiced with thespinal disc implant delivery devices described herein. As an example,the method may be practiced with device 800 as depicted in FIGS. 38-44.After implant 40 is deformed by, for example, manual force into asubstantially straightened, non-relaxed, unfolded, configuration forinsertion through an aperture formed in the annular fibrosis, it isloaded, or otherwise positioned in cavity 803 of syringe housing 802.Alternatively, as seen in FIG. 38, implant 40 may be straightened as itis inserted into cavity 803 at proximal end 804 of housing 802. Distalend 809 of plunger 806 may then be inserted into cavity 803 fromproximal end 804 of housing 802. Device 800, loaded with implant 40, maythen be positioned adjacent aperture 18 in annulus 19 as seen in FIG.40. Distal end 882 of movable members 880 are preferably positionedthrough aperture 18 in annulus 19 and preferably extend intointervertebral disc space 20 surrounded by annulus 19, as seen in FIG.40. Force is applied to plunger 806, preferably at its proximal end 807,to contact end 42 of implant 40 for translation of the implant towardsdistal end 812 of delivery tool 800. The force preferably will allowcontact of distal end 809 of plunger 806 with an adjacent end of theimplant and may be provided manually, with a mechanical pressurizationdevice, including a caulk gun, or by other devices and methods known tothe skilled artisan, including the force generator described in U.S.Pat. No. 5,800,849, as well as other hydraulic, pneumatic, manual orpower-assisted hydraulic force generators. It is noted that, whenutilizing device 700, 700′, 700″ or 700′″, the tip portion of thesedevices may act as a distractor to distract the disc space, although adistractor may also be used depending on the circumstances andpreference of the surgeon.

[0129] As implant 40 enters cavity 883 (cavity 883 being seen in FIG.36) defined by movable members 880 in their closed configuration,movable members 880 begin to move radially, or otherwise flex or bendradially, as seen in FIG. 41. Radial movement of movable members 880allows the movable members to contact the surrounding annular tissue andpress or otherwise push the tissue such that the annular defect, orother opening such as aperture 18, is dilated. This allows implant 40 toexit distal end 812 of delivery device 800 and enter intervertebral discspace 20 as seen in FIGS. 41-43, wherein movable members 880 are seen intheir open configuration.

[0130] As mentioned above, implants described herein having arms ofdifferential length can facilitate implantation and proper positioningof the implants in the intervertebral disc space. For example, such animplant having an off-center closure may prevent possible excessiverolling of the implant during insertion so that the implant will bepositioned such that the length of the implant extends substantiallyparallel to the coronal plane of a patient's body.

[0131] It is noted here that distal end 809 of plunger 806 may retainmovable members 880 in their open configuration as end 42 of implant 40approaches distal end 812 of delivery device 800 prior to completelyexiting the device. After the plunger is translated a sufficient amountdistally to allow implant 40 to exit the device, if necessary, theplunger is retracted, or translated in a proximal direction to ensurethe deforming members are in their closed configuration as seen in FIG.44. Delivery device 800 is then removed. As seen in FIG. 44, implant 40is properly positioned in intervertebral disc space 20.

[0132] Referring now to FIGS. 45-48, placement of the spinal implantdelivery devices having tip portions 710, 710′, 710″ and 710′″,respectively, in an intervertebral disc cavity 20, is shown. As can beseen in the figures, the distal ends of the tip portions preferablyextend slightly, e.g., about 1 mm to about 10 mm, past the inner face,or wall, I of annulus fibrosis 19. FIG. 49 is a view along line 49-49 ofFIG. 45 showing placement of tip portion 710.

[0133] The preferred delivery instrument, or device, and methodsdescribed herein are compatible with Medtronic Sofamor Danek's MetRX™microdiscectomy system and surgical procedures.

[0134] While the invention has been illustrated and described in detailin the drawings and foregoing description, the same is to be consideredas illustrative and not restrictive in character, it being understoodthat only the preferred embodiment has been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected. In addition, all references citedherein are indicative of the level of skill in the art and are herebyincorporated by reference in their entirety.

What is claimed is:
 1. An intervertebral disc nucleus pulposus implant,comprising: a load bearing elastic body sized for introduction into anintervertebral disk space, said body surrounded by a resorbable shell.2. An intervertebral disc nucleus pulposus implant, comprising: a loadbearing elastic body sized for introduction into an intervertebral discspace, said body surrounded by a supporting member, said supportingmember surrounded by a resorbable shell.
 3. An intervertebral discnucleus pulposus implant, comprising: a load bearing elastic body sizedfor placement into an intervertebral disc space, said body having afirst end, a second end, a central portion, and a first configurationwherein said first end and said second end are positioned adjacent tosaid central portion to form at least one inner fold, said elastic bodyconfigurable into a second, straightened configuration for insertionthrough an opening in an intervertebral disc annulus fibrosis, said bodyconfigurable back into said first configuration after said insertion. 4.The implant of claim 3, wherein said inner fold defines an aperture. 5.The implant of claim 3, wherein said elastic body is comprised of ahydrogel material.
 6. The implant of claim 3, wherein said elastic bodyis comprised of an elastomer.
 7. The implant of claim 6, wherein saidelastomer is selected from the group consisting of silicone,polyurethane, copolymers of silicone and polyurethane, polyolefins,nitrile and combinations thereof.
 8. The implant of claim 4, whereinsaid inner fold has a surface with projections, said projectionsextending into said aperture.
 9. The implant of claim 3, wherein saidelastic body has an outer surface, said outer surface having projectionsextending therefrom, said projections configured for enhancing fixationof said body in said intervertebral disc space.
 10. The implant of claim3, wherein the outer surface of said elastic body is microtexturized.11. The implant of claim 10, wherein said microtexturizing is performedby a process selected from the group consisting of bead blasting, plasmaetching, chemical etching and combinations thereof.
 12. The implant ofclaim 3, wherein said body further comprises a reinforcing material atsaid inner fold surface.
 13. The implant of claim 12, wherein saidreinforcing material comprises fibers.
 14. The implant of claim 3,wherein said elastic body is comprised of a hydrogel material, saidmaterial having at least one growth factor dispersed therein.
 15. Theimplant of claim 14, wherein said growth factor is selected from thegroup consisting of transforming growth factor β, bone morphogeneticproteins, fibroblast growth factors, platelet-derived growth factors,insulin-like growth factors and combinations thereof.
 16. The implant ofclaim 14, wherein said growth factor comprises a recombinant protein.17. The implant of claim 16, wherein said recombinant protein is a humanprotein.
 18. The implant of claim 3, wherein said body has at least onesurface depression in its second configuration, said inner fold formedfrom said surface depression.
 19. The implant of claim 3, wherein saidfirst end is formed from a first arm, said second end is formed from asecond arm and one of said arms of said implant has a length greaterthan the other of said arms.
 20. The implant of claim 4, wherein saidaperture has a cross-sectional shape selected from the group consistingof annular-shaped, elliptical-shaped, and star-shaped.
 21. The implantof claim 3, wherein said body is substantially elliptical- orring-shaped in its folded configuration.
 22. The implant of claim 3,wherein said body has a top surface for contacting an upper vertebralendplate of an intervertebral disc and a bottom surface for contacting alower vertebral end plate of an intervertebral disc, said top and bottomsurface configured to be complementary to the endplate they are incontact with.
 23. The implant of claim 22, wherein said top and bottomsurface of said body are convex.
 24. The implant of claim 3, whereinsaid first end and said second end each have an inner edge and an outeredge, at least one of said inner edges having a rounded configuration.25. The implant of claim 3, wherein said body has a top surface forcontacting an upper vertebral endplate of an intervertebral disc, abottom surface for contacting a lower vertebral end plate of anintervertebral disc, and an external side surface, said body having atleast one groove on said side surface, said groove extending betweensaid top surface and said bottom surface.
 26. An intervertebral discnucleus pulposus implant, comprising: a load bearing elastic body sizedfor placement into an intervertebral disc space, said body having afirst end and a second end, said first end and said second endconfigured for mating engagement with each other, said elastic bodyhaving a first configuration wherein said first end and said second endare matingly engaged to each other, said elastic body configurable intoa second, straightened configuration for insertion through an opening inan intervertebral disc annulus fibrosis, said body configurable backinto said first configuration after said insertion.
 27. A kit forforming an intervertebral disc nucleus pulposus implant, comprising aload bearing elastic body sized for introduction into an intervertebraldisc space and a container of material to form a resorbable shell aroundsaid body.
 28. A kit for forming an intervertebral disc nucleus pulposusimplant, comprising a load bearing elastic body sized for introductioninto an intervertebral disc space, a supporting member to surround saidbody and a container of material to form a resorbable shell around saidsupporting member.
 29. A method for implanting an intervertebral discnucleus pulposus implant in an intervertebral disc space, comprising:(a) preparing said intervertebal disc space to receive said implant; and(b) introducing a load bearing elastic body into said disc space, saidbody surrounded in said disc space by a resorbable shell.
 30. A methodfor implanting an intervertebral disc nucleus pulposus implant in anintervertebral disc space, comprising: (a) preparing said intervertebaldisc space to receive said implant; and (b) introducing a load bearingelastic body into said disc space, said body surrounded by a supportingmember, said supporting member surrounded in said disc space by aresorbable shell.
 31. A method for implanting an intervertebral discnucleus pulposus implant in an intervertebral disc space, comprising:(a) providing a load bearing elastic body sized for placement into anintervertebral disc space, said body having a first end, a second end, acentral portion, and a first configuration wherein said first end andsaid second end are positioned adjacent to said central portion to format least one inner fold, said elastic body configurable into a second,straightened configuration for insertion through an opening in saidannulus fibrosis, said body configurable back into said firstconfiguration after said insertion; (b) preparing said intervertebaldisc space to receive said body; and (c) positioning said body into saidintervertebral disc space after said preparing step.
 32. A method forimplanting an intervertebral disc nucleus pulposus implant in anintervertebral disc space, comprising: (a) providing a load bearingelastic body sized for placement into an intervertebral disc space, saidbody having a first end and a second end, said first end and said secondend configured for mating engagement with each other, said elastic bodyhaving a first configuration wherein said first end and said second endare matingly engaged to each other, said elastic body configurable intoa second, straightened configuration for insertion through an opening inan intervertebral disc annulus fibrosis, said body configurable backinto said first configuration after said insertion; (b) preparing saidintervertebal disc space to receive said body; (c) positioning said bodyinto said intervertebral disc space after said preparing step.
 33. Aspinal disc implant delivery device tip, comprising: (a) a base memberhaving a proximal end, a distal end and a lumen extending longitudinallytherethrough; and (b) a plurality of movable members, said movablemembers having a proximal end and a distal end, said proximal end ofsaid movable members abutting said distal end of said base member, saidmovable members having a closed configuration defining a cavity incommunication with said lumen of said base member, said members sizedand configured for passage into an aperture in an annulus fibrosis. 34.The tip of claim 33, wherein said lumen of said base member is sized toreceive a nucleus pulposus implant.
 35. The tip of claim 33, whereinsaid movable members have an open configuration wherein said movablemembers move radially.
 36. A spinal disc implant delivery device,comprising: (a) a base member having a proximal end, a distal end and alumen extending longitudinally therethrough; (b) a plurality of movablemembers, said movable members having a proximal end and a distal end,said proximal end of said movable members abutting said distal end ofsaid base member, said movable members having a closed configurationdefining a cavity in communication with said lumen of said base member,said movable members sized and configured for passage through anaperture in an annulus fibrosus; and (c) an elongated housing memberhaving a proximal end, a distal end and a lumen extending longitudinallytherethrough, said proximal end of said base member matingly engaged tosaid distal end of said elongated housing member.
 37. The device ofclaim 36, wherein said movable members have an open configuration whensaid movable members move radially.
 38. The device of claim 36, whereinsaid lumen of said elongated housing member is sized to receive anucleus pulposus implant.
 39. The device of claim 36, said devicefurther comprising a plunger member, said plunger member disposed insaid lumen of said elongated housing member.
 40. A spinal disc implantdelivery device, comprising: (a) an elongated housing member having aproximal end, a distal end and a lumen extending longitudinallytherethrough; (b) a tip member, said tip member having a top wall, abottom wall, a first side wall, a second side wall, a proximal end, anda distal end, said walls defining a lumen extending longitudinallytherethrough, said proximal end of said tip member connected to saiddistal end of said elongated housing member, said tip member sized andconfigured for delivery of a spinal disc implant through an aperture inan annulus fibrosus, said lumen of said tip member in communication withsaid lumen of said elongated housing member.
 41. The device of claim 40,said device further comprising a plunger member, said plunger memberdisposed in said lumen of said elongated housing member.
 42. The deviceof claim 40, wherein said top wall and said bottom wall both include anopening therethrough that extends from said proximal end of said tipmember to said distal end of said tip member.
 43. The device of claim42, wherein at least one of said top wall and said bottom wall has asurface that includes a surface roughening.
 44. The device of claim 43,wherein said surface roughening comprises teeth.
 45. The device of claim42, wherein one of said side walls has a length greater than the otherof said side walls.
 46. The device of claim 40, wherein at least one ofsaid top wall and said bottom wall has a surface that includes a surfaceroughening.
 46. The device of claim 40, wherein one of said side wallshas a length greater than the other of said side walls.